Baku, July 23, AZERTAC The same drought can devastate a plant’s flowering season or barely affect it at all, depending on when it occurs, according to a new Hebrew University study suggesting that scientists need to look beyond how much rainfall is lost and examine when drought strikes, according to TPS-IL.“Most people think that drought is simply less rain, but we discovered that its timing is also of enormous importance,” Barel Tsafon, a Ph.D. student at Hebrew University and one of the study’s lead researchers, told The Press Service of Israel.The study, published in the peer-reviewed Ecology Letters, found that droughts at different points in the growing season produced dramatically different effects on flowering — a stage critical to plant reproduction, pollinator survival and ecosystem health.The research was led by Tsafon and fellow Ph.D. student Or Gross, working under Prof. Niv DeMalach of the Faculty of Agriculture, Food and Environment at Hebrew University.To test how drought timing affects flowering, the team grew thousands of plants from five common Mediterranean species in a large greenhouse experiment. All the plants received identical reductions in water, but the drought was imposed either at the beginning, middle or end of the rainy season. Some plants were grown alone, while others were grown alongside neighboring species to examine how competition shapes their responses.The experiment produced two major findings. First, plants growing alongside other species shifted their flowering schedules so that each species tended to bloom at a different time, reducing the period when they flower at the same time and easing competition for resources. The researchers said the finding challenges the long-held assumption that species develop separate ecological roles — known as “niche separation” — only over evolutionary time, since it showed plants can adjust their flowering rapidly without any genetic change.Second, the timing of drought proved decisive. A five-week drought in mid-winter had surprisingly little effect, while droughts in autumn delayed flowering and droughts in spring caused plants to stop flowering earlier, shortening the flowering season significantly. Different species responded differently, highlighting the difficulty of predicting how ecosystems will respond to climate change.Asked why a mid-winter drought produced so little change while droughts at the start or end of the season caused major shifts, Tsafon told TPS-IL the timing corresponds to the most vulnerable stages of a plant’s life cycle.“A drought at the beginning or end of the rainy season is essentially an extension of the natural dry season, whereas a drought in the middle of the rainy season acts more like a temporary pulse of stress,” he said. “Our results suggest that these plants are particularly sensitive to drought at the beginning of the growing season, when germination and early establishment occur, and at the end of the season, when they shift resources from vegetative growth to seed production.”Tsafon added that studying species in isolation, as many climate change experiments do, can produce misleading results. “Neighboring species can alter a plant’s sensitivity and response to climate change, so preserving and restoring entire plant communities, not just individual species, may be important for maintaining ecosystem resilience,” he told TPS-IL.DeMalach said the mechanism behind the pattern is likely simple competition for water rather than any coordinated behavior among plants. “Plants do not communicate like humans and do not make decisions about when it is best to bloom in order to avoid getting in trouble with more attractive plants,” he said. “One plant takes water from another plant, and because of the resulting water shortage, the neighboring plant has fewer resources. This shortage forces it to start flowering later or finish flowering earlier.”The researchers said the findings highlight the need for scientists and conservationists to consider not only how much rainfall ecosystems receive, but also when it occurs. Protecting entire plant communities, rather than focusing only on individual species, may be key to maintaining ecosystem resilience as the climate changes.